The repository changes with each release and I am not sure how backwards compatible (if at all) the repo is. Next you need to determine which version they are on and what version they are trying to move back to. In my opinion, the potential to mess up a production environment is high.
This is one of those questions that is not easily answered in a few sentences. Once you determine why they are doing a rollback you can see if this is better suited for Support to handle.